This section provides background information related to the present disclosure which is not necessarily prior art.
Pneumatic valve assemblies are well known in the art for controlling the flow of pressurized air or liquids. One type of pneumatic valve currently employed in numerous applications in the related art is generally known as a poppet valve. Poppet valves find particular use in connection with pilot operated pneumatic valves as a part of an overall fluid powered system. One common poppet valve arrangement includes a valve member movably supported within a valve body between predetermined positions. These positions are typically defined by the placement of the seats within the valve bore. The valve member has a valve element that engages the seats.
One consideration to maintaining a consistent valve member stroke and thereby valve longevity is the nature of the seat and valve member interaction. Valve seats commonly employed in the related art typically include a square cut or 90° corner surface. The corresponding valve element usually includes a relatively conical or angularly-formed valve sealing surface. Most often, the valve element is over-molded, or encapsulated, with a resilient material to improve the sealing effect and provide a slight cushioning of the valve member as it interacts with the squared valve seat. The square cut 90° corner of the valve seat can penetrate deep into the poppet valve element during valve operation. As it penetrates, the force being applied to the valve element is spread out across the valve-sealing surface. This sealing interaction initially tends to create a good seal as the over-molded material on the sealing surface of the valve element deflects inwardly slightly as it rests against the edge of the seat thereby creating a ring seal about the seat. However, this sealing effect creates wear as the valve is repetitively activated by causing the sealing material to be repetitively deformed and ultimately damaged, for example by being cut as the valve member moves to its seated position against the square cut valve seat during each and every valve closing event.
As the sealing material begins to permanently deform and then finally cut, the actuator must make a longer and longer stroke to seal the valve. This on-going lengthening of the valve stroke introduces a dynamic change to the timing of the valve actuation, which degrades the operation being performed. Changes in valve timing actuation due to changes in the valve stroke translate into process inaccuracies and inconsistencies that ultimately require valve replacement. Secondly, the deforming and cutting of the valve sealing material may cause leakage and often introduces pieces of the sealing material into the downstream pneumatic flow path.